A 70-year-old woman presents with rapidly enlarging pelvic mass and ascites. Endometrial biopsy shows high-grade carcinoma with comedo-type necrosis, marked nuclear atypia, and slit-like spaces. Immunohistochemistry is positive for p53 (mutant pattern), negative for ER/PR, and shows HER2 overexpression (3+ on IHC). What is the most likely histologic type and the associated targeted therapy option?
- A Endometrioid adenocarcinoma; pembrolizumab
- B Clear cell carcinoma; bevacizumab
- C Uterine serous carcinoma; trastuzumab ✓
- D Carcinosarcoma; pazopanib
Correct answer: C. Uterine serous carcinoma; trastuzumab
Explanation
The histologic features (high-grade nuclei, comedo necrosis, slit-like spaces) and immunoprofile (mutant p53, loss of ER/PR, HER2 overexpression) are classic for uterine serous carcinoma. Approximately 30% of uterine serous carcinomas overexpress HER2. The NRG-GY018 trial showed benefit of trastuzumab added to chemotherapy for HER2-positive uterine serous carcinoma. Pembrolizumab is for MSI-H/dMMR tumors. Bevacizumab is not specific to clear cell carcinoma. Pazopanib is used for soft tissue sarcomas, not carcinosarcoma as primary therapy.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.